So 3 changes: started using FreeStyle Libre and change of diet about the same time, followed by a reduction in meds.
Started using Libre - I wouldn't think the Libre would be the issue.
But it can be part of the solution. It can take readings every minute and store 8 hours worth. What are those trends showing after eating until you get up?
The change in diet - possibly.
Reduction of carbs would lower BG.
Only eating one meal a day (wasn't a change) Just eating would be a cause for an initial insulin response, even without carbs. Whats going on after you eat?
Eating the sacks of chips looks like it too has been followed with a lowering of BG into the 60s, but after a spike.
The milk didn't get same response of going lower. Lactose metabolizes slower? More insulin resistant at that time of day?
The reduction in the meds possibly a contributor but not the cause (possibly not enough reduction a cause?)
Glimepiride stimulates the pancreas to release more insulin (needed or not??). May enhance the normal calls for insulin (over response??)
It is supposed to start working as soon as it is metabolized (usually within first 4 hours)
The timing of meds. I read where glimepiride is recommended to take with the first main meal of the day. Not sure of lasting effects of daily dose but it seems your dose is taken at the other end of the 24 hour clock from your late night/early morning lows. Timing may not be a issue.
Dose - maybe your carb reduction was greater than your insulin reduction and that is lowering your BG after a meal.
It is also a possibility that this was going on before the changes but not discovered until the Libre.
Looks like more questions arise. Sounds like homework time. Might let the doctor know and see if he would agree to stop the glimepiride and watch the results. He may be able to tell you how long it would be working after you stopped it. He might appreciate being in the loop, he might not.